Molecule-based transistor using

A Molecule-based Transistor Using Conducting Polymers... 

Tumer-Jones, E.T. Chyan, O.M. Wrighton, M.S. Preparation and characterization of molecule-based transistors with a 50-nm source-drain separation with use of shadow deposition techniques Toward faster, more sensitive molecule-based devices. J. Am. Chem. Soc. 1987, 109. 5526-5528. 

Wrighton and co-workers developed a "molecule-based transistor" which uses conducting polymers either chemically doped polyaniline layers deposited atop Au interdigitated electrodes [44] or on 50-100 nm "gate" polyaniline polymer between two Au electrodes shadowed with Si02 this device still has a rather slow switching rate (10 kHz) and a gain of almost 1,000 [45]. The related work of Stubb and co-workers is discussed elsewhere in this volume. 

Single molecule Cgo based transistors were also fabricated by depositing a diluted Cgo toluene solution onto a pair of gold electrodes. The whole structure was built on an insulating Si02 layer on top of a doped Si wafer that was used as the gate electrode to modulate the electrostatic potential of the Cgo molecule trapped in the middle of the junction (see Fig. 14). The observed 1-V characteristics were... 

Electronic noses The so-called electronic noses consist of chemical gas sensors that are able to monitor changes in the offgas composition of fermentation processes. The different sensors of electronic noses are based on conductive polymers (CP), metal oxide semiconductors (MOS), metal oxide semiconductor field effect transistors (MOSFET), or quartz crystal microbalance (QCM). CP-based sensors use the electrochemical properties of polymers like polypyrrole or polyindole. The absorbance of selected molecules of the off-gas into the polymer film causes changes in the sensors conductivity. MOS sensors possess an electrochemically active surface of metal oxides like tin oxide or copper oxide. The sensitivity... 

Other alternatives for the construction of CNT based FETs have been explored. For example, carbon nanotube branches with Y shape can be used directly as transistors where the modulation of the current from an ON to an OFF state is presumably mediated by the defects and the morphology of the junction (see Fig. 19) [170, 171]. Carbon nanotube based FETs can be gated by an electrode immersed in a solution, or by charged molecules in solution (proteins, DNA, etc.) which opens a huge field of applications in sensors [172-176] (see Fig. 20). Their ability to operate under biological conditions allows their direct use or integration into biological systems [177]. 

Fig. 2. Resistivity-vs.-temperature transition curves for some C j based superconductors. (A) Variation of the hole doping from 1.3 to 3.2 holes per C o molecule. Inset the field-effect transistor geometry used in the experiment. (B) Comparison of optimum hole-doped C ). as grown and intercalated with CHCI3 and CHBrj)...

Pd MOS STRUCTURES The Pd MOS device (capacitor and field effect transistor) has been extensively studied as a model chemical sensor system and as a practical element for the detection of hydrogen molecules in a gas. There have been two outstanding reviews of the status of the Pd MOS sensor with primary emphasis on the reactions at the surface (7,8). In this section, the use of the device as a model chemical sensor will be emphasized. As will be seen, the results are applicable not only to the Pd based devices, they also shed light on the operation of chemfet type systems as well. Because of its simplicity and the control that can be exercised in its fabrication, the discussion will focus on the study of the Pd-MOSCAP structure exclusively. The insights gained from these studies are immediately applicable to the more useful Pd-MOSFET. 

---